Railway track

ABSTRACT

In a vehicle track having longitudinal rail members positioned in parallel on either side of a track centerline and on which respective drive wheels and guide wheels of a vehicle move, the improvement including longitudinal rail members each having an asymmetrical cross-section and being composed of a head portion having a primary upper running face which engages the periphery of the drive wheel, a lower guide face opposed to the primary upper running face which engages the guide wheel, and a secondary running face which is substantially vertical, which is located inwardly of the head portion towards the track centerline, and which engages the flange of the drive wheel; and a leg portion extending downwardly from the head portion; and a plurality of track support members arranged at intervals along the vehicle track and composed of a clamp device having first and second clamp faces which are moveable, which are juxtaposed to the leg portion one on each side thereof, which grip the leg portion, and which each incorporate a resilient element comprised of elastomeric material interposed between the leg portion and the respective clamp face.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a railway track for an automatedguided vehicle system. Whilst the invention is, according to oneembodiment, directed towards and primarily described with reference tosuch systems, it is considered that the invention is suitable for usewith other guided vehicle systems used, for example, for freighttransportation or materials handling. The invention in a preferred formrelates to the reduction of noise during operation of such systems.

2. Description of the Related Art

An automated guideway system of the above type is described inco-pending PCT Application No. PCT/AU94/00201 entitled "Rail GrippingVehicle". As described therein, such a system utilising individualvehicles which each accommodate, for example, between eight andtwenty-five passengers would typically operate on guideways separatedfrom other vehicular traffic and pedestrians. Such guideways willpreferably be narrow, elevated above street level and supported onpillars, an arrangement often referred to as a monorail. The systemshould desirably operate with low noise and vibration levels.Preferably, the vehicles should descend and ascend on ramps fromguideways to the street level and be capable of very short emergencystopping distances if they are to operate safely at high speeds andclose intervals.

Generally, in systems of the type referred to, vehicles have pneumatictire wheels which operate directly on the concrete or other guidewaysurface, and are therefore acceptably quiet. However, their stopping andgrade climbing ability is unsatisfactory as is also their maximum speed.The guideways are frequently unacceptably wide.

In order to meet the various requirements referred to above, the systemdescribed in the above referenced PCT application employs steel wheelson the vehicles operating on narrow track steel rails; secondary railgripping wheels which press on the underside of the railhead runningface are used so increasing the grip of the main wheels on the rails inorder to meet the necessary accelerating, braking, and ramp climbingcapabilities. These wheels need only be engaged when slippage of themain drive wheels is likely, and at other times remain slightly clear ofthe rail surface. In such a position they guard against possiblederailment of the vehicle in high winds or other disturbances which canprove hazardous for narrow gauge systems. However, attention has to bepaid to minimising noise and vibration inevitably associated with theuse of steel wheels. Such noise is particularly apparent when thevehicle is traversing curved track due to contact between the wheelflanges and the rail. This aspect of the problem is addressed in theco-pending PCT Application AU95/00046 "Self Steering Railway Bogie"which describes an arrangement which greatly reduces flange contact,even in small radius curves. A feature of that invention is the use ofsteeply inclined wheel axes and rail running faces to produce thesteering action.

The rumbling sound which originates in slight rail and wheel surfaceirregularities and in the drive system, both in curved and straighttrack, also needs to be considered. This problem occurs in conventionallight railways and street cars using steel wheels and rails, and it iscommon practice to incorporate rubber pads in the wheels to reduce thetransmission of contact noise from the wheel rims to the wheel disk fromwhich it is radiated. This principle is also adopted in the presentinvention.

Such noise is also transmitted to the rails, and it is accepted railwaypractice to stand the rails on base plates insulated from the trackfoundation by resilient mountings as illustrated in AU42628/78 (531212)B(Duchemin).

SUMMARY OF THE INVENTION

The present invention consists in a longitudinal rail member for avehicle track in combination with a plurality of track support membersarranged at intervals along the track, the rail member comprising a headportion having a primary upper running face and a substantially verticalsecondary running face located inwardly of the rail head towards thetrack centreline adapted to engage respectively the periphery and flangeof the vehicle wheel, said head portion having a lower guide faceopposed to said primary upper running face and a leg portion extendingdownwardly from said head portion substantially adjacent to saidsecondary running face characterised in that each said support memberhas clamp means having first and second relatively movable facesjuxtaposed one on each side of said leg portion, adapted to grip saidleg portion, each face incorporating a resilient elastomeric materialelement interposed between said leg portion and said face.

Preferably the elastomeric material is substantially faced with a metalliner which engages with the leg portion of the rail.

Preferably the leg portion of the rail has a foot portion for engagementof the track support members.

In a second aspect the invention comprises a rail having an upper facefor the main wheels to run on, a lower opposed face for the grip wheelto run on, and a substantially vertical face for the flange of the mainwheel set to engage. The above faces are grouped together in closeproximity and incorporated in the head of the rail. Preferably they arearranged in the form of a ledge which extends outwardly with respect tothe track centreline from the body of the rail which takes the form of adownwardly extending leg attached to brackets spaced along the track.The means of attachment includes clamp jaws, one on each side of the legof the rail each lined with a resilient material such as rubber.

Such an arrangement allows the resilient material to be located well upthe leg itself and adjacent to the underside of the rail head so thatthe resilient material is loaded in shear rather than in compressionwith respect to the vertical loads, and hence may be relatively soft,yet is loaded in compression with respect to the lateral load and henceis relatively rigid. Because of the small vertical offset between therail head and the resilient material, side forces applied to the railhead such as from wheel flange contact produce only small deflections,particularly as the material is in compression in the lateral direction.

Thus the arrangement shown in Duchemin, which is typical of the practicewidely used to suppress noise in main line railway practice, is totallyunsuited to use in the small, rail gripping vehicle to which the presentinvention relates. A relatively more resilient mount is required tosuppress the vibrations which originate not only in the main wheels butalso in the grip wheels. Note that the rail has to be of about the sameheight as in the case of the main line rail in order to provideclearance so that the underslung grip wheels in order that they clearthe sleepers. Furthermore, if a flange were used at the bottom of therail web or leg, it could only extend inwardly, for the same reason. Aresilient mount placed so far below the head of the rail and so faroffset from the plane in which the rail head forces (i.e., the normalforce at wheel contact, and flange forces, if any) are aligned, wouldresult in the two rails splaying apart under load.

A preferred arrangement is to employ at regular intervals along thetrack a shoe or bracket rigidly secured to the guideway or trackfoundation which has a face which is inwardly inclined towards thecentre of the track to match the angle of the leg of the rail. To thisface is bonded a rubber insulating layer of substantially uniformthickness arranged to bear directly on the outer face of the rail leg.The bracket extends inwardly horizontally towards the centre of thetrack to provide a guide for a wedge clamp piece also having aninsulating layer of rubber bonded to its face which bears directly onthe inner face of the rail leg. One or more clamp bolts passing the apexof the wedge clamp serve to apply considerable pressure to the rubberinsulating layers to inhibit the longitudinal sliding of the rail. Byputting the rubber bond under compressive stress it is less likely toprogressively separate from the surface to which it is bonded, aprecautionary measure which is well known in the art. The bonded layerof rubber on the bracket may extend around and underneath an enlargedfoot of the rail leg so that it cannot move downwardly more than theamount permitted by the shear of the bonded rubber layer.

Because the leg portion of the rail is laterally offset from the ledgeportion, it can be somewhat shorter than if it had to extend below thebottom of the secondary wheel, thus minimising the area of the railexposed to the air and hence the degree to which noise originating inrail-wheel contact is radiated to the air.

In a still further embodiment, thin sheet metal plates are bonded to theinner faces of the rubber isolation blocks to avoid direct contactbetween them and the rail leg. The sheet metal plate of the bracket isbent around so as to neatly conform to the enlarged foot of the railleg.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be better understood a preferred formthereof is hereinafter described, by way of example, with reference tothe accompanying drawings, in which:

FIG. 1 shows a cross-sectional elevation through a guideway and rails,and an end view of a bogie arrangement;

FIG. 2 shows an enlarged part-sectional view of the wheels, rail, railsupport bracket and tie;

FIG. 3 is a plan view of the rail support bracket; and

FIG. 4 is an enlarged view of Section X--X of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows the general features of a vehicle bogie and track accordingto one aspect of the invention. Vehicle 1 is supported on bogie 2 bysuspension members 50, which include linkages for the control of therelative lateral, longitudinal and roll motions.

Main drive wheels 3 rotate on axles whose axes 4 are inclined to thehorizontal and engage the upper face of rails 5 which are provided withupper and lower inclined running faces. In FIG. 2 axes 4 of main drivewheels 3 are inclined to the horizontal about 20 degrees. It should benoted however, that inclination in the range of 10 to 30 degrees may beemployed when used in conjunction with the "Self Steering Railway Bogie"of PCT/AU94/00046.

In FIG. 2 grip wheel 6 is shown disengaged from the lower running faceof the rail 5, but may be raised to press thereon as described in PCTApplication No. AU94/00201 in order to increase the grip of the mainwheel 3 on rail 5 during grade climbing or emergency braking.

Rail 5 is clamped in bracket 7 secured to guideway beam 8 by bolts 51(see FIG. 3) symmetrically about track centreline 7a and is maintainedat a correct spacing by sheet metal tie 9.

Referring now to FIG. 2, wheel 3 having axis 4 comprises rim 10 whichincorporates disc hub 11 having an array of holes 12 therein forretention of circular rubber damping members 13 which are forconvenience, bonded to sheet metal sheathing cups 14. At their outerextremities parallel to axis 4, cups 14 enter wheel flange member 15secured to hub 3a of wheel 3. This construction of a drive wheel is wellknown in the art, for example UK Patent No. 1,199,897.

Similarly, grip wheel 6 which rotates freely on an axle of axis 35,comprises rim 16, rubber isolating ring 17 and hub 16a, as is well knownin the art.

Rail 5 comprises ledge (or head) portion 18, leg 19 and foot 20 andaccording to the arrangement shown, it is firmly gripped in bracket 7which is provided with an upwardly extending inwardly inclined face 21to which is bonded a rubber isolation strip 22, which itself is bondedto sheet metal liner 23.

Ledge portion 18 has upper surface 18a for the main wheel 3 to run on, alower surface 18b for the grip wheel 6 to run on and a substantiallyvertical face 18c for the flange of rim 10 to engage. Leg 19incorporates a bend at 19a to provide clearance between grip wheel 6 andbracket 7 when the bogie is negotiating curves of small radii. Uppersurface 18a is inclined with respect to lower surface 18b in order tofacilitate clearance between grip wheel 6 and bracket 7.

Foot 20 of leg 19 aids in locating the rail vertically within thebracket 7. Sheet metal liner 23 is curved about foot 20 which willassist in preventing sheet metal liner 23 from moving upwardly in theclamp in the event that the bond between inclined face 27 and rubberisolation strip 22 should fail. Rubber isolation strip 22 extends into ahorizontal portion 22a of bracket 7 and is moulded so as to allow a gap25 to provide increasing vertical stiffness of the clamp as the downwardtravel of the rail under load exceeds the width of gap 25.

Wedge clamp 26 has rubber isolation strip 27 and sheet metal liner 28bonded thereto in a manner similar to isolation strip 22 and sheet metalliner 23 of bracket 7.

Screws 30 are tightened according to a specification that determines thelongitudinal force associated with slippage, which can be transmittedfrom rail 5 to bracket 7 before slippage occurs.

Thus if it is desired to have rail 5 welded into continuous lengths inorder to eliminate the noises associated with rail joints, thenexpansion and contraction forces resulting from the relative expansionof rail 5 with respect to guideway 8 must be resisted by the brackets.Such forces reach a maximum value at the ends of a long length of weldedrail, for example, where a track switch occurs, and should be less thanthe above slippage force. The prevent such forces reaching a value thatcould affect the bonding of the rubber isolation strips 22 and 27, forexample during periods of extreme temperatures, the ends of sheet metalliners 23 and 28 (refer to FIG. 4) are bent around at right angles ateach end of bracket 7, and suitable gaps 31 and 32 are provided to limitsuch travel whilst still providing a resilient mounting under normalcircumstances. Gaps 31 and 32 are provided at each end of bracket 7 asshown in FIG. 3.

It will be seen that both the rubber elements 22 and 27 and the sheetmetal liners 23 and 28 are so configured that even in the event of afailure of the bonding occurs, they can not escape from the clampconfiguration either vertically upwards or longitudinally along thedirection of the track.

It should be noted that rail 5, whilst being asymmetrical incross-section as compared to conventional rail sections, is configuredsuch that it does not assume curvature in the vertical plane when bentin the horizontal plane; this is because the neutral axis, shown as Y--Yin FIG. 2 is vertical as installed.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

What is claimed is:
 1. In a vehicle track having longitudinal railmembers positioned in parallel on either side of a track centerline andon which respective drive wheels and guide wheels of a vehicle move, theimprovement comprising:longitudinal rail members each having anasymmetrical cross-section and being comprised of: a head portion havinga primary upper running face which engages the periphery of the drivewheel, a lower guide face opposed to the primary upper running facewhich engages the guide wheel, and a secondary running face which issubstantially vertical, which is located inwardly of the head portiontowards the track centerline, and which engages the flange of the drivewheel; anda leg portion extending downwardly from the head portion; anda plurality of track support members arranged at intervals along thevehicle track and comprised of clamp means having first and second clampfaces which are moveable, which are juxtaposed to the leg portion one oneach side thereof, which grip the leg portion, and which eachincorporate a resilient element comprised of elastomeric materialinterposed between the leg portion and the respective clamp face.
 2. Thevehicle track according to claim 1, wherein the first and second clampfaces are substantially inclined inwardly towards the centerline of thetrack, and wherein the primary upper running face is substantiallyinclined downwardly toward the centerline of the track.
 3. The vehicletrack according to claim 2, wherein the clamp means further comprises ametal liner provided between each respective resilient element and theleg portion, at least one of the metal liners having a transverseportion which engages a portion of the leg portion and which precludingdownward movement of the leg portion with respect to the metal linerwhile permitting longitudinal movement therebetween.
 4. The vehicletrack according to claim 3, wherein the transverse portion comprises asubstantially horizontal ledge extending horizontally immediatelybeneath the leg portion of the longitudinal rail member.
 5. The vehicletrack according to claim 1, wherein each of the resilient elements isfaced with a metal liner where it engages the leg portion of thelongitudinal rail member.
 6. The vehicle track according to claim 1,wherein the resilient elements are each bonded to respective clampfaces.
 7. The vehicle track according to claim 6, wherein the metalliners are provided with edge flanges which prevent movement thereof inrelation to the clamp faces so that deflection of the resilient elementsin the longitudinal direction of the track is substantially prevented.8. The vehicle track according to claim 1, wherein one clamp face fromamong the first and second clamp faces of respective track supportmembers is fixed and another clamp face from among the first and secondclamp faces of respective track support members is movable.